At Monte Alban, I love the Black Mole (although the other moles are good)- rich flavor, really what oaxacan food is about, the Tacos Enchilados - a bit more traditional us-mex, the Empanadas de Huitlachoche, and the pork dish (forget the exact name, something abodabo).

As suggested above, I'd stick to the basics - mole negro ("black mole") - with chicken. This is the Oaxacan dish that has spread around the Americas, and to me, a pretty good yardstick to judge the quality of the place. I've actually had bad luck ordering other dishes at Guelaguetza (and a couple others) - grilled pork ribs that were totally dry and barely warm - sort of like you'd expect at a ribs, pizza and wings place (maybe an off day?). And I wouldn't make too concerted an effort to eat "healthy" at a Oaxacan place - just have a salad for another meal that day. A friend of mine ordered an entree w/ nopales at a mole place I really like and got just that - a fairly bland pile of sliced cactus.

There are several varieties of mole sauce, but some of these may be indistinguishable with what we know as sort of pan-Mexican sauces, e.g., red mole may just resemble the red sauce of chile colorado at other Mexican restaurants. Lots of places have antojitos (appetizers) that cover a decent range of the dishes, so maybe get a couple of those for the table. And, don't forget the drinks. The fruits are more varied and exotic as you get farther down into Mexico, so you might find some good punches and things that can make the meal memorable.

At Monte Alban, I think they have a few dishes that are very good. Their guacomole is excellent, so you can start with that. Get some queso fundido, as well -- it's a great combo. For entrees, I think their clayudas, tortas, and mole dishes are excellent. They have a couple dishes with huitlacoche that are particularly good. I have also had their ceviche and I generally liked it, though it was not the best I've had in LA or the best thing I've eaten there. I have seen other people eat the daily special of seafood in a molcajete and it looks outstanding.